Did you try the 200% setting on the iq8?
Building a PV Shedding Controller for AC Coupled Solar
- Thread starter wheisenburg
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wheisenburg
Independent Solar Consultant
I need to know if there is a 200% / Hz profile that is IQ8 compatible. I found an "Off Grid" profile that is supposed to AC Couple with Schneider, but it says it is compatible with the IQ7 family only.
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Can you also show the grid codes setting? The freq-watt (and volt-watt, etc.) curtail curve (including the frequency shift limits and resolution) is dependent on the grid code setting. It could help explain why the AC Coupling SOC limit didn't work as expected.
wheisenburg
Independent Solar Consultant
Well I did more testing today. Based on prior testing I adjusted the load shedding so that string 1 sheds at 92% SOC and reattaches at 90%. String 2 sheds at 97% and reattaches at 94%. String 3 is now always connected.
The AC Coupled Frequency Shifting can manage the 3 KW output of string 3 with no issues. Before I disconnected the first two strings in one phase and the final string in the other. That is not needed.
I ran my drier, dishwasher, and oven and got the SOC down to 80%. I actually had to turn off the PV circuit breakers in the Envoy or it would not drain the battery due to all the PV. Then I turned the PV breakers back on. My dryer cycles the element on and off and so does my oven. Anyway it charged the batteries up to 92% pretty quickly. Then the charging rate backed down until 97%. At that point string 2 shed and the system was nearly balanced with some battery drain. The oven wasn't on anymore. So string 2 cycled on a couple of times. Once the drier and dishwasher were done, it actually got to 100% and killed string 3 through frequency shifting. It came back on in 5 minutes.
So I am very happy. This system handled everything I threw at it. I was pulling 6k each from the inverters for a while. They didn't even get warm that I could tell. I was charging at 160 amps. I believe I now have things working good. I am ready for an outage if we ever get one. The last piece is a generator for the winter time. I have an energy gap un Dec, Jan, and Feb. Three more batteries would help, but my system just doesn't produce enough in the winter.
Finally, there were some questions as to whether AC Coupled charging was "stackable". Some people said Schneider was still working on that. I ran into no issues. The inverters seem to switch seamlessly from inverting to AC coupled charging and sharing the loads across both inverters with no issues.
Frankly, based on my testing, if I needed to run my dryer on a sunny day during a grid outage, I would be fine doing that as long as I waited till the batteries were full. I ran 4 loads of laundry today.
The AC Coupled Frequency Shifting can manage the 3 KW output of string 3 with no issues. Before I disconnected the first two strings in one phase and the final string in the other. That is not needed.
I ran my drier, dishwasher, and oven and got the SOC down to 80%. I actually had to turn off the PV circuit breakers in the Envoy or it would not drain the battery due to all the PV. Then I turned the PV breakers back on. My dryer cycles the element on and off and so does my oven. Anyway it charged the batteries up to 92% pretty quickly. Then the charging rate backed down until 97%. At that point string 2 shed and the system was nearly balanced with some battery drain. The oven wasn't on anymore. So string 2 cycled on a couple of times. Once the drier and dishwasher were done, it actually got to 100% and killed string 3 through frequency shifting. It came back on in 5 minutes.
So I am very happy. This system handled everything I threw at it. I was pulling 6k each from the inverters for a while. They didn't even get warm that I could tell. I was charging at 160 amps. I believe I now have things working good. I am ready for an outage if we ever get one. The last piece is a generator for the winter time. I have an energy gap un Dec, Jan, and Feb. Three more batteries would help, but my system just doesn't produce enough in the winter.
Finally, there were some questions as to whether AC Coupled charging was "stackable". Some people said Schneider was still working on that. I ran into no issues. The inverters seem to switch seamlessly from inverting to AC coupled charging and sharing the loads across both inverters with no issues.
Frankly, based on my testing, if I needed to run my dryer on a sunny day during a grid outage, I would be fine doing that as long as I waited till the batteries were full. I ran 4 loads of laundry today.
wheisenburg
Independent Solar Consultant
This is a trace from this weekend's test. From 10:00 to 1:30 the graph shows string 3 running and string 2 cycling on and off to supply the load from my dryer and other heavy loads. Even with this 5000 watt load running, it can keep the battery between 94 and 100% SOC. The dryer is not a steady load. It cycles on and off to maintain a certain temperature. I wanted to be able to test what would happen with all three strings running. The PV was keeping up even with my large loads, so I turned all the PV breakers off. From 1:30 to 2:15 of the trace here shows running the dryer and oven with all the PV circuits turned off. This was so I could deplete the battery below 90%. This is required to get the third string to turn on. Then at 2:15 to 2:45 all 3 strings are turned on when I turned the PV breakers back on. All three strings were running and the battery charged back up quickly. From 2:45 to 6:00 the graph again shows string 3 running and string 2 cycling on and off to maintain a more steady state condition after all the big loads were finished. The last current spike around 6:00 PM is from turning the grid back on and the resulting charge cycle.
Pushing large amounts of current in and out of the battery does cause them to heat up a little, but the voltage and the SOC stay well controlled despite large swings in current. Once the batteries were charged up, the PV shedding occurred. Then when the system was maintaining a more steady state and not running huge loads, the batteries were no longer heating up. Also, the SOC is maintained at a fairly high level. Sol Arc recommends setting their system up so AC coupling will turn on at 80% and off at 90%. This means that you could go into the night time at only 80% charge if your timing is bad. If you reserve 10% to prevent an unrecoverable "black start" during an outage, you would have only 70% usable charge or 10.5 KWHs going into the night.
Ideally, I would still like to be at 6 batteries rather than 3, but I am calling this a success. Running over night assuming conservative power usage should be fine with this setup. If an outage occurs in summer, I should be fine to run the A/C until around 7:00 PM. I might program the thermostat to "Pre-cool" the house the last 3-4 hours of the day and then turn the A/C off between 7 PM and 7 AM. The running watts on my A/C is around 2000 Watts so it is no problem running it while sunny. My house should stay cool enough overnight in PA given our climate. With 6 batteries, I probably wouldn't need to change anything.
In the winter, with only 8 hours of generation, I might use 8 KWHs overnight just for idle consumption. So useable capacity should be around 15K * 0.85 = 12.75 KWH. I should be able to make it through the 16 hour night, but I will need to supplement once a day with a generator when it is cloudy. If I charge the batteries up every evening when they are low, I should be fine. Being able to keep the battery more fully charged is almost like getting another 1/2 of a battery usable. If I had 6 batteries, the Sol Arc charging model would mean I could lose pretty much an entire battery of usable charge each night.
Pushing large amounts of current in and out of the battery does cause them to heat up a little, but the voltage and the SOC stay well controlled despite large swings in current. Once the batteries were charged up, the PV shedding occurred. Then when the system was maintaining a more steady state and not running huge loads, the batteries were no longer heating up. Also, the SOC is maintained at a fairly high level. Sol Arc recommends setting their system up so AC coupling will turn on at 80% and off at 90%. This means that you could go into the night time at only 80% charge if your timing is bad. If you reserve 10% to prevent an unrecoverable "black start" during an outage, you would have only 70% usable charge or 10.5 KWHs going into the night.
Ideally, I would still like to be at 6 batteries rather than 3, but I am calling this a success. Running over night assuming conservative power usage should be fine with this setup. If an outage occurs in summer, I should be fine to run the A/C until around 7:00 PM. I might program the thermostat to "Pre-cool" the house the last 3-4 hours of the day and then turn the A/C off between 7 PM and 7 AM. The running watts on my A/C is around 2000 Watts so it is no problem running it while sunny. My house should stay cool enough overnight in PA given our climate. With 6 batteries, I probably wouldn't need to change anything.
In the winter, with only 8 hours of generation, I might use 8 KWHs overnight just for idle consumption. So useable capacity should be around 15K * 0.85 = 12.75 KWH. I should be able to make it through the 16 hour night, but I will need to supplement once a day with a generator when it is cloudy. If I charge the batteries up every evening when they are low, I should be fine. Being able to keep the battery more fully charged is almost like getting another 1/2 of a battery usable. If I had 6 batteries, the Sol Arc charging model would mean I could lose pretty much an entire battery of usable charge each night.
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